Gas blast circuit breaker of the axial blast type with means for injecting a high velocity gas jet



P. BARKAN GAS BLAST CIRCUIT BREAKER OF THE AXIAL BLAST TYPE WITH MEANS FOR INJECTING A HIGH VELOCITY GAS JET Filed Nov. 21, 1963 5 Sheets-Sheet l //v VENTOR PHIL/P BAR/m N, 5y Mu -w M A TTOR/VE) Aug. 30, 1966 P. BARKAN 3,270,173

GAS BLAST CIRCUIT BREAKER OF THE AXIAL BLAST TYPE WITH I MEANS FOR INJECTING A HIGH VELOCITY GAS JET Flled Nov. 21, 1963 5 Sheets-Sheet 2 AX/AL VELOC/T) //V OR/F/CEOFF/G 2 INVENTOR. PHIL/P BAR/(AN,

ATTORNEY Aug. 30, 1966 P. BARKAN 3,270,173

GAS BLAST CIRCUIT BREAKER OF THE AXIAL BLAST TYPE WITH MEANS FOR INJECTING A HIGH VELOCITY GAS JET Filed Nov. 21, 1963 3 Sheets-Sheet 5 //v VENTOR. PH/L/P BAR/(AN,

5y ATTORNEY United States Patent 3,270,173 GAS BLAST CIRCUIT BREAKER OF THE AXIAL BLAST TYPE WITH MEANS FOR INJECTING A HIGH VELOCITY GAS JET Philip Barkan, Lima, Pa., assignor to General Electric Company, a corporation of New York Filed Nov. 21, 1963, Ser. No. 325,236 9 Claims. (Cl. 200-148) This invention relates to a gas blast circuit breaker of the axial blast type and, more particularly, to means for improving the interrupting ability of such a circuit breaker.

The usual gas blast circuit breaker comprises means for establishing an electric arc across a gap between two electrodes and means for directing a high velocity blast of gas into the arcing region. The purpose of the gas blast is to cool the arc and to scavenge the arcing region of arcing products so as to increase the rate at which dielectric strength is built up across the gap when the current zero point is reached. By increasing this rate of dielectric recovery, it is possible to improve the ability of .the gap to withstand the usual recovery voltage transient which builds up as soon as current zero is reached, thus improving the interrupting ability of the circuit breaker.

In an axial blast type of circuit breaker, there is typically provided an orifice through which the are between the electrodes extends and through which the gas blast flows axially of the are about the periphery of the arc. The purpose of the orifice is to guide the blast with respect to the arc and to impart the desired high velocity to the blast. The electrode that is located upstream from the orifice is referred to hereinafter as the upstream electrode and the electrode that is located downstream from the orifice is referred to hereinafter as the downstream electrode.

In the typical axial blast circuit breaker, there is a stagnation zone on the downstream side of the upstream electrode. The gas blast that flows past the upstream electrode toward the orifice opening separates from the surface of the upstream electrode adjacent its downstream side and creates this stagnation zone radially inwardly of the region at which such separation occurs. Typically, the gas blast forces the upstream terminal of the are into the stagnation zone and holds it captive therein. From an interrupting ability viewpoint, this is not an ideal position in which to maintain the upstream arc terminal. Both the scavenging process and the arc cooling process are ordinarily relatively inefficient in the stagnation zone, because the gas in this zone tends to move in large scale eddies of relatively low velocity; and this low velocity detracts from both scavenging and are cooling.

An object of the present invention is to increase the efiiciency of both the scavenging and the arc-cooling processes in this zone at the downstream side of the upstream electrode.

Another object is to produce a large radial gradient in the axial velocity of the gas entering the orifice opening, so .as to create high shear stresses that produce intense turbulence to accelerate the arc-cooling process.

'In carrying out my invention in one form, I provide a gas blast circuit breaker that comprises an upstream electrode, a downstream electrode, and an orifice having an opening positioned between said electrodes. During an interrupting operation, an arc is established between the 3,270,173 Patented August 30, 1966 electrodes that extends through the orifice opening, and a blast of gas is caused to flow through the orifice opening via paths extending along the external surface of the up stream electrode and generally axially of the are adjacent said upstream electrode. The upstream electrode has a downstream surface facing the orifice opening; and extending through this surface I provide a passageway that is directed toward the orifice opening. Means is provided for directing a jet of gas through said passageway into said orifice opening. This jet of gas is developed while the previously-described blast is flowing through the orifice opening, and the blast generally surrounds the jet. Means is provided for imparting to the jet a velocity, as it enters said orifice opening, that is substantially higher than the velocity of the gas surrounding it so that high shear stresses are present at the interface of the jet and said blast to produce intense turbulence that accelerates arc cooling.

For a better understanding of my invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross sectional view of a portion of an axial blast circuit breaker embodying one form of my invention.

FIG. 2 is a cross sectional view of certain parts of a conventional axial blast circuit breaker.

FIG. 3 is a cross sectional view of a portion of the circuit breaker of FIG. 1 taken during an interrupting operation.

FIG. 3a illustrates a modified form of my invention.

FIG. 4 is a graphical representation of certain velocity relationships occurring with the conventional circuit breakerof FIG. 2.

FIG. 5 is a graphical representation of the same velocity relationships in the circuit breaker of FIGS. 1 and 3.

FIG. 6 is a sectional view illustrating another modified form of my invention.

FIG. 7 is an enlarged sectional view illustrating still another modified form of my invention.

FIG. 8 is a reduced-size view, partially in section,

I showing in more detail how the structure of FIG. 1 is included in a circuit breaker assembly.

Referring now to FIG. 1, the circuit interrupter shown therein is of the sustained-pressure, gas-blast type described and claimed in US. Patent 2,78 3,-33 8Beatty, assigned to the assignee of the present invention. Only those parts of the interrupter that are considered necessary to provide an understanding of the present invention have been shown in FIG. 1. In this respect, only the right hand portion of the interrupter has been shown in section inasmuch as the interrupter is generally symmetrical with respect to a vertical plane and the left hand portion -is substantially identical to the right hand por tion. As described in detail in the above-mentioned Beatty patent, the interrupter comprises a casing 12 which is normally filled with pressurized gas to define an interrupting chamber 11. Located within the interrupting chamber 11 are a pair of relatively movable contacts 1-4 and 16 which can be separated to draw an are within the pressurized gas within the chamber 11. The contact 14 is relatively stationary, whereas the other contact 16 is mounted for pivotal motion about a fixed, current-carrying pivot 18. When the movable contact 16 is driven clockwise about the pivot 18 from its solidline closed position of FIG. 1, an arc is established in the region where the contacts part. The movable con-tact 16 is shown by dotted lines in FIG. 1 in a partially-open position through which it passes during a circuit-interrupting operation after having established an arc.

The movable contact 1 6 is supported by means of its current-carrying pivot 18 on .a conductive bracket 19 that is preferably formed integral with a stationary cylinder 3 2. The cylinder 32 at its lower end is suit-ably supported from a generally cylindrical casting 33. The casting at its lower end is suitably secured to a flange 35 rigidly carried by the stationary metallic casing 12.

'For producing a gas blast to aid in extinguishing the arc, the cylindrical cast-ing 33 contains a normally-closed exhaust passage 36 leading from the interrupting chamber 11 to the surrounding atmosphere. The casting 33 at its upper end is provided with a tubular nozzle member 38 having an orifice portion 39 at its outer end defining an inlet 37 to the exhaust passage 36. This inlet 37 is referred to hereinafter as the orifice opening. The flow of arc-extinguishing gas through the tubular nozzle 38 and the exhaust passage 36 is controlled by means of a cylindrically-shaped reciprocable blast valve member 40 located at the outer, or lower, end of the exhaust passage 36. This blast valve member 40 normally occupies a solid-line, closed position wherein an annular flange 42 formed at its lower end sealingly abuts against a stationary valve seat 34 carried by the exhaust cast-ing 33.

During a circuit interrupting operation, the movable blast valve member 40 is driven upwardly from its solidline, closed position of FIG. 1 through a partially open intermediate position shown in dotted lines in FIG. 1. Opening of the valve member 40 allows pressurized gas in the chamber 11 to flow at high speed through the oritfice opening 3 7 and nozzle 38 and out the exhaust passageway 36 past the valve member 48 to atmosphere, as indicated by the dotted line arrows B of FIG. 1. The manner in which the gas blast acts to extinguish the arc will soon be described in greater detail.

At is upper end, the cylindrical blast valve member 48 surrounds a projecting tubular support 41 upon which the valve member 40 is smoothly slid able. The tubular support 41 is fixed to the casting 33 by suitable means (not shown). A compression spring 44 positioned between the movable valve member 40 and the lower end of support 41 tends to hold the valve member 40 in its closed position against the valve seat 34.

To protect the support 41 and the upper end of the valve member 40 from the harmful effects of arcing, a protective metallic tube 43 is positioned about these parts and is suitably secured to the support 41. Secured to the outer surface of this tube is a downstream probe or electrode 45, preferably of a refractory metal, which projects radially from the tube 43 and transversely into the path of the gas blast flowing through the passageway 36. As will soon appear more clearly, the downstream terminal of the arc is transferred to this electrode 45 during an interrupting operation and, after such transfer, occupies a position generally corresponding to that shown at 46. The downstream electrode is preferably constructed as shown and claimed in Patent No. 2,897,- 324Schneider, assigned to the assignee of the present invention, so that it has a non-streamlined upstream surface 48 that coacts with the gas blast to form a stagnation region upstream from the surface 48. The terminal of an are such as 46 reaching the electrode 45 is captured within the stagnation region and thus prevented from being driven further downstream by the gas blast.

For controlling the operation of the movable blast valve 40 and movable contact 16, a combined operating mechanism 50 is provided. This mechanism 50 is preferably constructed in the manner disclosed and claimed in the aforementioned Beatty Patent 2,783,338, and its details form no part of the present invention. Generally speaking, this mechanism 50 comprises a blast valvecontrolling piston 51 and a contact-controlling piston 52 mounted within the cylinder 32. The blast valve-controlling piston 51 is coupled to the movable blast valve member 40 through a piston rod 54 suitably clamped to the valve member 40. The contact-controlling piston 52, on the other hand, is connected to the movable contact 16 through a piston rod 58 and a cross head 59 secured to the piston rod. A link 60 pivotally joined to the cross head 59 at 61 and to the movable contact 1 6 at 62 interconnects the cross head 59 and the movable contact 16. When the blast valve-controlling piston 51 is driven upwardly, it acts to open the blast valve member 40, and, simultaneously, to drive the contact-controlling piston 52 upwardly to produce opening movement of the movable contact member 16.

Opening movement of the contact member 16 first establishes an are between the ends of the contacts 14 and 16. Shortly thereafter, however, the blast of gas which has been flowing through the orifice opening 37, as indicated by the dotted-line arrows B, forces the upstream terminal of the are on to an upstream arcing electrode 70, which is electrically connected to the stationary contact 14. As opening motion of the movable contact 16 continues, the gas blast forces the downstream terminal of the arc to transfer from the movable con tact 16 to orifice structure 39, which is electrically connected to the movable contact 16. The gas blast then impels the downstream terminal of the are through the orifice opening 37 and nozzle 38 on to the upper end of the protective metallic tube 43. From there, the gas blast drives the downstream arc terminal downwardly and into the previously-described stagnation region adjacent the downstream surface 48 of the electrode 45. The are then occupies the position generally shown in 46. When the arc is in this position, the arc column extends through the orifice opening 37 and is subjected in the orifice region to an intense high velocity blast. This blast is effective to cool and deionize the arc and to prevent reignition thereof at an early current zero.

It is generally understood that the ability of the circuit breaker to prevent the arc from reigniting at a current zero depends upon the rate at which dielectric strength is recovered across the arcing region when arcing ceases at current zero. The faster the dielectric recovery rate, the lowe the chance for reignition and thus the better the chances for successful interruption at this point.

I have found that substantial improvements in this dielectric recovery rate can be made by eliminating the stagnation zone that has existed at the downstream face of the upstream electrode and by converting this zone into one that is characterized by high velocities and large radial gradients in the axial velocity that produce intense turbulence. This intense turbulence promotes rapid cooling of the arc plasma, thus improving the dielectric recovery rate. Also, the high velocities contribute to efficient and rapid scavenging, thus further improving the dielectric recovery rate.

The stagnation zone referred to in the immediately preceding paragraph is illustrated in FIG. 2, which shows a conventional upstream electrode B being enveloped by an axial blast of gas. The primary flow paths followed by the gas blast as it streams past the upstream electrode E are designated B. As shown in FIG. 2, these paths B follow the external contour of the electrode E .rather closely about the outer periphery of the electrode but eventually separate from. the surface of the electrode at points designated S in FIG. 2 near the outer periphery of the downstream face of the electrode E. Radially inwardly of these points S there is a zone 74 in which the gas flows at relatively low velocities in large scale eddies such as depicted at 75. This zone 74 is referred to herein as the stagnation zone.

The upstream terminal of an are established between the contacts 16 and 14 is transferred from the contact 14 onto the upstream electrode 70 by the gas balst following the paths B. The gas blast then drives the upstream terminal in the direction of the gas blast into the stagnation zone 74. As pointed out hereinabove, this is not an ideal position for the arc terminal since the gas in this zone is flowing in large scale eddies 75 at relatively low velocities, and these low velocities detract from both scavenging and arecooling.

In accordance with the present invention, I effectively eliminate the stagnation zone by directing a high velocity jet of gas from an ultra high pressure source through the above-described location of the stagnation zone from the upstream electrode 70 into the orifice opening 37. This jet is shown in FIG. 3 at 76 passing through a central opening 77 in the upstream electrode 70. This jet 76 is derived from a pressure source (soon to be described) that is at a much higher pressure than the pressure of the gas in the tank 12 following the path B. In a preferred embodiment of my invention, the source from which the jet 76 is derived is at a pressure of 1500 p.s.i., as compared to a normal pressure inside the tank 12 of 500 p.s.i. This high pressure jet 76 has a velocity that is much higher than the velocity of the gas that is following path B.

One of the effects of this high velocity jet is to cause the blast B to adhere more closely to the downstream surface of the upstream electrode 70. In this regard, an education action by the jet shifts the separation points S radially inwardly as compared to their location in FIG. 2, so that they are located immediately adjacent jet 76. This virtually eliminates the previously-described stagnation zone 74.

Another effect of the high velocity jet 76 is to produce a large radial gradient in the axial velocity of the gas entering the orifice opening 37, and this large radial gradient results in high shear stresses at the interference between the jet 76 and the main blast B, which produce intense turbulence. This intense turbulence promotes cooling of the arc plasma. To explain this effect further, the approximate axial velocity of the gas passing through the main orifice opening 37 has been plotted in FIGS. 4 and 5. Curve V in these figures (4 and 5) represents the axial velocity of the gas blast considered at different radii of the orifice opening. FIG. 4 illustrates the axial velocity V for a conventional arrangement such as shown in FIG. 2, whereas FIG. 5 illustrates the axial velocity V for the arrangement of FIG. 3 where the high velocity jet 76 is present.

Referring to FIG. 4, it will be noted that the axial velocity V considered at all radii from the center of the orifice opening to a point near the orifice boundary changes only slightly. This is further illustrated by curve dV /dr which depicts the first derivative or slope of curve V which is referred to hereinafter as the radial gradient of the axial velocity V In FIG. 4, this radial gradient is quite small and uniform in the central region of the orifice opening and increases abruptly only when the orifice boundary is approached.

Referring to FIG. 5, it will be noted that the axial velocity V follows a radically different pattern when the jet 76 is present. Here the axial velocity V is much higher at the center of the orifice opening and drops abruptly just a short distance from the center. In terms of the radial gradient dV /dr, there is a high radial gradient only a short distance from the center line of the orifice opening, as illustrated by the sharp rise in the curve dV /dr to its peak. 80. This high radial gradient results in high shear stresses, and these high shear stresses produce intense turbulence in the central region of the orifice. These high shear stresses exist along an extended portion of the arc length back to a point closely adjacent the upstream electrode 70. Thus, there is intense turbulence along an extended portion of the arc length to further accelerate cooling of the arc plasma.

If the central jet, instead of having a velocity much higher than that of the gas following paths B, had a velocity substantially equal to the velocity of such gas,

then the axial velocity V in the orifice would be substantially as shown in FIG. 4. In other words, there would be only a slight radial gradient and slight shear stresses and little resulting turbulence in the crucial central region of the orifice opening. It will therefore be apparent that an important part of the invention embodied in FIGS. 1 and 3 is in using a jet that has a velocity much higher than the velocity of the gas following paths. B.

The fact that the jet 76 is in a downstream direction and is a very high velocity jet is advantageous for the additional reason that it promotes the scavenging that is needed to force ionized arcing products out of the stressed region between the electrodes 70 and 45.

For initiating and terminating the jet 76, I provide an auxiliary valve located within the hollow upstream electrode 70. This valve 85 comprises a movable valve member 86 that is biased by a spring 87 into a closed position shown in FIG. 1 against its seat 89. The auxiliary valve 85 is a pressure sensitive valve that opens in response to a pressure differential of a predetermined value on opposite sides of the valve member 86 and closes when this differential falls below another predetermined value. In a specific embodiment of my invention the valve 85 is normally subject to 500 p.s.i. gas on its downstream side and 1500 p.s.i. gas on its upstream side. The spring 87, which bears at its rear end against a nut 88 carried by the movable valve member 86, holds the valve member 86 in its closed position against the force resulting from this pressure differential and is adapted to maintain the valve closed until the pressure differential exceeds, say 1050 psi.

If the main blast valve 42 is opened, gas flow B through the orifice opening 37 causes a drop in the local static pressure on the downstream side of the movable valve member 86, and the pressure differential on opposite sides of the valve member 86 thus rises to a value above'lOSO p.s.i. This causes the valve member 86 to move leftwardly to its open position of FIG. 3, allowing ultra high pressure gas to flow past the valve member 86 and through a central opening 77 in the downstream face of electrode 70. This flow creates the ultra high pressure jet 76 described hereinabove. The fully-open position of the valve 85 is determined by a perforated member 92 attached to the movable valve member 86 and engageable with a fixed abutment 91 when the valve member reaches its fully open position.

When the main blast valve 42 closes after the arc is extinguished, pressure in the tank 12 quickly builds up, and this reduces the pressure differential on opposite sides of the movable auxiliary valve member 86, thus causing the movable valve member 86 to close and terminate the jet 76.

For supplying the ultra high pressure gas that is used for the jet 76, I provide a reservoir 99 within the conductor 100 that carries current to and from the electrode 70. This conductor 100 is a tubular member that has an enlarged hollow portion 101 at its outer end, as shown in FIG. 8. The interior of this tubular conductor 100 serves as the reservoir 99, and the enlarged portion 101 provides added capacity for the reservoir.

The hollow conductor 100 is supported on the tank 12 and is insulated therefrom by means of a hollow porcelain shell 104 that surrounds the conductor as shown in FIGS. 1 and 8. As best seen in FIG. 1, the reservoir 99 in the conductor 100 communicates with the interior of hollow electrode 70 through a passageway 107 that is provided in an adaptor 108 of conductive material that supports the upstream electrode 70 and the stationary contact 14. When the jet-controlling valve 85 is opened, pressurized gas flows from the reservoir 99 through the valve 85 via paths such as depicted by the dotted-line arrows 112 of FIG. 1.

The overall system is filled by supplying pressurized gas at 1500 p.s.i. to the ultra high pressure reservoir 99 through a suitable supply line 114 shown in FIG. 8. The jet-controlling valve 85 and the main blast valve 42 are then closed. The pressure in the ultra high pressure chamber will build up until it exceeds the pressure in the tank 12 by at least 1050 p.s.i. When this occurs,. valve 85 will open and gas will jow therethrough into the tank 12. The valve 85 remains open until the pressure in the tank 12 by at least 1050 p.s.i. When this occurs, valve set to close when the pressure differential on its opposite sides falls below 950 p.s.i., the valve 85 will then close. A pressure relief valve 120 is preferably provided to bleed the excess pressure above 500 p.s.i. from the main tank 12. This pressure relief valve 120 will open after the jet controlling valve 85 closes and will thus reduce the pressure in tank 12 to its normal 500 p.s.i. value, at which point the pressure relief valve will close.

Although I prefer to inject the ultra high pressure gas through a single central opening 77, as shown in PEG. 3, I may in certain cases provide a plurality of closely spaced openings through which the high pressure gas is injected toward the main orifice opening 37 in the form of a plurality of jets. Such an arrangement is shown in FIG. 3a, where the plural openings in the upstream electrode are designated 77a, and the individual high velocity jets issuing from these openings are designated 76a. The main blast is designated B. These openings 77a are located near the central region of the electrode 70 so that the jets are generally surrounded by the main blast B, in much the same manner as in FIG. 3.

An alternative scheme for operating the valve 85 is shown in FIG. 6. Here the valve 85 is controlled independently of the pressure in tank 12 and by a pilot valve 130. This pilot valve 130 controls the pressure inside a pilot chamber 132 located behind a piston 134 coupled to the movable valve member 86. The pilot valve has two positions, one in which it vents the pilot chamber 132 to a low pressure region and one in which it connects the pilot chamber 132 to a source of high pressure. The pilot valve 130 is shown in FIG. 6 in its first or venting position. When the pilot valve is in this position, the spring 87 forces the movable valve member 86 into its closed position shown. When the pilot valve member 138 is shifted counterclockwise, it interconnects a high pressure line 136 and the pilot chamber 132, thus forcing the piston 134 and valve member 86 to the left to open the valve 85. Ultra high pressure gas fiows from a line 137 past the valve member 86 when the valve member 86 is open. Closing of the valve member 86 is effected by returning the pilot valve 130 to its illustrated position to vent the space behind the pilot piston 134. The pilot valve 130 is controlled by suitable electrical controls (not shown), which cause it to produce opening of the valve member 86 when the circuit breaker is opened and closing of the valve member 86 when the interrupting operation is completed. This alternative arrangement has the advantage of operating fully independently of the pressure in the interrupter tank 10.

FIG. 7 illustrates a modified upstreamelectrode 70 that corresponds in most respects to the electrode 79 of FIGS. 1 and 3 but differs therefrom in that means is provided for injecting into the main blast stream B a high velocity boundary flow 140 that is directed along the downstream surface of the electrode 70. For producing this boundary flow 140, I provide an annular defiector 142 that surrounds the upstream electrode and is suitably secured thereto. Internally of this deflector 142 is an annular space 144 that communicates with the interior of the hollow electrode 70 through a series of peripherally spaced holes 145 located downstream from valve member 86. When the valve member 86 is moved to open position, pressurized gas flows past the valve member 86, through the holes 145 and the space 144, and along the downstream surface of the electrode 70, as shown at 140. This injected boundary flow 140 is in 8 addition to the jet 76, which is directed through the central opening 77, and the main flow depicted at B.

With the injected boundary flow 1 40 present, the velocity of the gas moving in the immediate vicinity of the electrode surface is substantially higher than that velocity which would be present without the injected boundary flow. This higher velocity results in improved scavenging of the downstream surface of the electrode 70 and further reduces the changes for any appreciable stagnation zone developing at this location.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A gas blast circuit breaker comprising:

(a) a chamber containing a gas at a first pressure,

(b) an upstream electrode and a downstream electrode located within said chamber,

(c) an orifice having an opening positioned between said electrodes,

(d) means for establishing an arc between said electrodes that extends through said orifice opening,

(e) blast valve means downstream from said orifice and operative when said arc is established for causing a blast of gas from said chamber to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and generally axially of said are adjacent said upstream electrode,

(f) said upstream electrode having a downstream surface constituting a portion of said external surface and facing said orifice opening when an arc is present between said electrodes,

(g) a reservoir containing high pressure gas at a pressure substantially higher than said first pressure,

(h) a passageway leading from said reservoir through said downstream surface of the upstream electrode and directed toward said orifice opening,

(i) a normally closed auxiliary valve between said reservoir and said passageway,

(j) and means for opening said auxiliary valve upon establishment of said are to force a jet of said high pressure gas through said passageway into said blast and toward said orifice opening,

(k) said jet having a velocity as it enters the orifice opening that is substantially higher than the velocity of said blast surrounding the jet so that high shear stresses are present at the jet periphery to produce intense turbulence.

2. A gas blast circuit breaker comprising a chamber containing gas at a first pressure and further comprising:

(a) an upstream electrode and a downstream electrode located within said chamber,

(b) an orifice having an opening positioned between said electrodes,

(c) means for establishing an are between said electrodes that extends through said orifice opening,

(d) means operative when said are is established for causing a blast of gas to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and generally axially of said arc adjacent said upstream electrode,

(c) said upstream electrode having a downstream surface constituting a portion of said external surface and facing said orifice opening when an arc is present between said electrodes,

(f) a passageway leading through the downstream surface of said upstream electrode and directed toward said orifice opening,

(g) means operative when said blast is flowing through said orifice opening for directing a jet of gas through said passageway and said orifice opening that is gen erally surrounded by said blast,

(h) said jet having a velocity as it enters the orifice opening that is substantially higher than the velocity of said blast surrounding the jet so that high shear stresses are present at the jet periphery to produce intense turbulence,

(i) and a reservoir for supplying gas to said passageway for said jet, said reservoir containing gas at a pressure higher than said first pressure.

3. A gas blast circuit breaker comprising a chamber containing gas at a first pressure and further comprising:

(a) an upstream electrode and a downstream electrode located within said chamber,

(b) an orifice having an opening positioned between said electrodes,

(c) means for establishing an are between said electrodes that extends through said orifice opening,

((1) means operative when said are is established for causing a blast of gas to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and generally axially of said are adjacent said upstream electrode,

(c) said upstream electrode having a downstream surface constituting a portion of said external surface and facing said orifice opening when an arc is present between said electrodes,

(f) a plurality of passageways leading through the downstream surface of said upstream electrode and directed toward said orifice opening,

(g) means operative when said blast is flowing through said orifice opening for directing jets of gas through said passageways and said orifice opening that are generally surrounded by said blast,

(h) said jets having a velocity as they enter the orifice opening that is substantially higher than the velocity of the adjacent blast so that high shear stresses are present at the jet periphery to produce intense turbulence,

(i) 'a reservoir for supplying gas to said passageways for said jets, said reservoir containing gas at a pressure higher than said first pressure.

4. A gas blast circuit breaker comprising:

(a) an upstream electrode and a downstream electrode,

(b) an orifice having an opening positioned between said electrodes,

() means for establishing an are between said elec trodes that extends through said orifice opening,

(d) means operative when said are is established for causing a blast of gas to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and generally axially of said are adjacent said upstream electrode,

(c) said upstream electrode having a downstream surface facing said orifice opening,

(f) a passageway leading through the downstream surface of said upstream electrode and directed toward said orifice opening,

(g) means operative when said blast is fiowing through said orifice opening for directing a jet of gas through said passageway and said orifice opening that is generally surrounded by said blast,

(h) means for imparting to said jet a velocity as it enters the orifice opening that is substantially higher than the velocity of said blast surrounding the jet so that high shear stresses are present at the jet periphery to produce intense turbulence,

(i) a normally-closed valve controlling the flow of gas through said passageway,

(j) a high pressure reservoir communicating with said passageway for supplying gas for said jet,

(k) and means for operating said valve to an open position in response to a predetermined difference in the reservoir pressure and the pressure in a zone adjac nt 10 said downstream surface of the upstream electrode.

5. The circuit breaker of claim 2 in combination with:

(a) a normally-closed valve controlling the flow of gas through said passageway,

(b) and valve-control means for operating said normallly-closed valve to an open position during an interrupting operation of said circuit breaker.

6. .A gas blast circuit breaker comprising:

(a) an upstream electrode and a downstream electrode,

(b) an orifice having an opening positioned between said electrodes,

(0) means for establishing an are between said electrodes that extends through said orifice opening,

(d) means operative when said are is established for causing a blast of gas to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and generally axially of said are adjacent said upstream electrode,

(c) said upstream electrode having a downstream surface facing said orifice opening,

(f) a passageway leading through the downstream surface of said upstream electrode and directed toward said orifice opening,

(g) means operative when said blast is flowing through said orifice opening for directing a jet of gas through said passageway and said orifice opening that is generally surrounded by said blast,

(h) means for imparting to said jet a velocity as it enters the orifice opening that is substantially higher than the velocity of said blast surrounding the jet so that high shear stresses are present at the jet periphery to produce intense turbulence,

(i) a normally-closed valve controlling the flow of gas through said passageway,

(j) a high pressure reservoir communicating with said passageway for supplying gas for said jet when said normally-closed valve is open, and

(*k) valve-control means for operating said normallyclosed valve to an open position during an interrupting operation of said circuit breaker, said valvecontrol means comprising a pilot valve that is operable to control operation of said normally-closed valve.

7. The gas blast circuit breaker of claim 2 in combination with means for injecting independently of said blast a boundary flow of gas along said downstream surface of said upstream electrode that increases the gas velocity in the immediate vicinity of said downstream surface as compared to that which would be present without said independently-injected boundary How of gas.

8. A gas blast circuit breaker comprising:

(a) an upstream electrode .and a downstream electrode,

(b) an orifice having an opening positioned between said electrodes,

(c) means for establishing an are between said electrodes that extends through said orifice opening,

(d) means operative when said arc is established for causing a blast of gas to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and axially of said arc adjacent said upstream electrode,

(e) said upstream electrode having a downstream surface constituting a portion of said external surface and facing said orifice opening when an arc is present between said electrodes,

(f) means for ejecting independently of said blast a boundary flow of gas along said downstream surface of said upstream electrode that increases the gas velocity in the immediate vicinity of said downstream surface as compared to that which would be present without said independently-injected boundary flow of gas.

9. The circuit breaker of claim -8 in which said injecting means comprises a deflector having an inlet and an outlet, said outlet being directed generally parallel to said downstream surface, and means for supplying gas for said 2,981,815 4/1961 Leeds et a1. 200148 boundary flow to said inlet 3,150,245 9/1964 Leeds 61 a1. 200145 R f Ct d b h E FOREIGN PATENTS e e y e xamme 5 358,554 10/1931 Great Britain.

UNITED STATES PATENTS 2 7 117 3 1957 Forwald 200 148 ROBERT K SOHAEFER, Primary Examiner. 2,897,324 7/1959 Schneider 200-148 ROBERT S. MACON, KATHLEEN H. CLAFFY, 2,924,690 2/1960 Browne et a1. 20082 X Examiners. 

1. A GAS BLAST CIRCUIT BREAKER COMPRISING: (A) A CHAMBER CONTAINING A GAS AT A FIRST PRESSURE, (B) AN UPSTREAM ELECTRODE AND A DOWNSTREAM ELECTRODE LOCATED WITHIN SAID CHAMBER, (C) AN ORIFICE HAVING AN OPENING POSITIONED BETWEEN SAID ELECTRODES, (D) MEANS FOR ESTABLISHING AN ARC BETWEEN SAID ELECTRODES THAT EXTENDS THROUGH SAID ORIFICE OPENING, (E) BLAST VALVE MEANS DOWNSTREAM FORM SAID ORIFICE AND OPERATIVE WHEN SAID ARC IS ESTABLISHED FOR CAUSING A BLAST OF GAS FROM SAID CHAMBER TO FLOW THROUGH SAID ORIFICE OPENING VIA PATHS THAT EXTEND ALONG THE EXTERNAL SURFACE OF SAID UPSTREAM ELECTRODE AND GENERALLY AXIALLY OF SAID ARC ADJACENT SAID UPSTREAM ELECTRODE, (F) SAID UPSTREAM ELECTRODE HAVING A DOWNSTREAM SURFACE CONSTITUTING A PORTION OF SAID EXTERNAL SURFACE AND FACING SAID ORIFICE OPENING WHEN AN ARC IS PRESENT BETWEEN SAID ELECTRODES, (G) A RESERVOIR CONTAINING HIGH PRESSURE GAS AT A PRESSURE SUBSTANTIALLY HIGHER THAN SAID FIRST PRESSURE, (H) A PASSAGEWAY LEADING FROM SAID RESERVOIR THROUGH SAID DOWNSTREAM SURFACE OF THE UPSTREAM ELECTRODE AND DIRECTED TOWARD SAID ORIFICE OPENING, (I) A NORMALLY CLOSED AUXILIARY VALVE BETWEEN SAID RESERVOIR AND SAID PASSAGEWAY, (J) AND MEANS FOR OPENING SAID AUXILIARY VALVE UPON ESTABLISHMENT OF SAID ARC TO FORCE A JET OF SAID HIGH PRESSURE GAS THROUGH SAID PASSAGEWAY INTO SAID BLAST AND TOWARD SAID ORIFICE OPENING, (K) SAID JET HAVING A VELOCITY AS IT ENTERS THE ORIFICE OPENING THAT IS SUBSTANTIALLY HIGHER THAN THE VELOCITY OF SAID BLAST SURROUNDING THE JET SO THAT HIGH SHEAR STRESSES ARE PRESENT AT THE JET PERIPHERY TO PRODUCE INTENSE TURBULENCE. 